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External Combustion Engines: Open & Closed Cycles

Types of Gas Power Cycles:

Open Cycles

Internal Combusion (IC)

vs.

Closed Cycles

External Combustion (EC)

External Combustion

In an

external combustion cycle

, the combustion process does not take place within the system.
The hot gases from the combustion process provide heat to the power cycle through a heat exchanger.

In a

closed gas power cycle

, the working fluid is recirculated.

The

closed gas power cycle

with

external combustion

is generally only used as a model to simplify the analysis of the

open gas power cycle

. In practice, most

gas power cycles

are open.

Lesson
9E Blog

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Lesson 9E: page 3 of 16

In an external combustion cycle, the combustion reaction does NOT take place inside the power cycle system.
Instead, the hot exhaust gases from the combustion reactor exchange heat with the working fluid in HEX #1.
External combustion is effective in both open and closed cycles, as shown here.
So, if external combustion and closed gas power cycles are uncommon, why do we study them ?
We study them because they are easier to analyze but still retain all of the important features of open, internal combustion engines.
The result is that we end up with a group of equations that we are capable of solving in a reasonable time AND these equations demonstrate all of the most important trends exhibited by the more complicated open, internal combustion cycles.

External Combustion Engines: Open & Closed Cycles

external combustion cycle

closed gas power cycle

closed gas power cycle

external combustion

open gas power cycle

gas power cycles

Ch 9, Lesson E, Page 3 - External Combustion Engines: Open & Closed Cycles